The present invention relates to a tree stump grinding apparatus for disintegrating wood material.
Conventional stump grinders are disclosed in U.S. Pat. Nos. 6,382,277 and 6,546,977, for example. Typically, the stump grinder includes a rotatable wheel or disc having a plurality of side cutting teeth projecting from the side surfaces of the disc and peripheral cutting teeth spaced about an outer peripheral edge surface of the disc. Each of the side and peripheral cutting teeth includes a cutting head, having a cutting edge. In use, the disc is driven about a horizontal axis, whereupon the cutting heads of the side and peripheral teeth contact and gradually disintegrate a stump.
It is desirable for the peripheral cutting teeth to be disposed at different respective angular orientations relative to the plane of the disc to provide maximum coverage with each rotation of the disc. To achieve that multi-orientation feature in a device such as disclosed in U.S. Pat. No. 6,382,277, wherein the holder for the peripheral cutting teeth are actually mounted in the side surfaces, it is necessary to provide peripheral cutters that are different from one another, which increases manufacturing and inventory costs. To achieve the multi-orientation feature in a device such as disclosed in U.S. Pat. No. 6,546,977, wherein the holders for the peripheral cutting teeth are mounted on the floors of respective recesses formed in the disc's peripheral edge surface, it is necessary to move each holder in two directions relative to an adjacent holder in order to properly position the peripheral cutting teeth, which represents an undesirably complex maneuvering.
In U.S. Pat. No. 4,530,385, a stump cutter is disclosed (see FIG. 1) which includes a disc 10 having side cutter teeth 12s and two circumferentially spaced peripheral cutter assemblies 12p disposed in respective recesses 18 formed in the disc's outer peripheral surface. Each cutter assembly comprises a holder 20 and a peripheral cutting tooth 30 mounted in the holder. Each holder is attached to leading and trailing (i.e., circumferentially spaced) walls 22, 24 of the recess. The two holders 20 shown in FIG. 1 are tilted in opposite respective directions, i.e., to the right and left sides of the disc. A shank 31 of each peripheral cutter tooth 30 extends through a hole in the holder and is tightly secured thereto by a fastener nut 32 which is threaded onto the shank with the intention of rendering the tooth immovable. However, during a stump-cutting operation, strong loads will be applied not only to the tooth, but also to the nut, which is exposed. That is, the nuts may be contacted by a stump, or rocks, dirt, etc., disposed adjacent to the stump, causing the nuts to loosen and eventually cause the cutter teeth to become loosened or even lost.
Also, each outer peripheral tooth 12p typically has a flat cutter surface 34 facing in the direction of rotation. Such a configuration of the cutter surface is ideal for cutting through wood fibers, but is highly vulnerable to chipping, cracking and breaking when rocks are encountered.
Therefore, it would be desirable to provide a stump cutter which minimizes or obviates existing shortcomings.
It would be further desirable to provide a stump cutter in which the fastener nuts of peripheral cutter teeth are protected against being turned and loosened during cutting operations.
A further object is to provide teeth that are less susceptible to being chipped, broken, or cracked by rocks.
Another object is to simplify the act of orienting teeth at different angular orientations on a disc.